—Mark Guagliardo, Veterans Health Administration
The Veterans Health Administration (VHA) geocodes the residential addresses of approximately 8.5 million enrolled healthcare beneficiaries annually to support system planning efforts for the nation's largest integrated healthcare system. Until recently the appropriateness of the spatial distribution of VHA facilities was assessed by overlaying enrollee point locations with facility service area polygons. Drive time band values, e.g. 0–30, 30–60 minutes, were assigned to enrollees. Crude statistics such as the percentage of enrollees within 30 minutes of VHA primary care could be calculated. To improve the power, precision and insight of statistical analyses of access to care we endeavored to estimate precise drive time and distance to nearest VHA facility for all 8.5 million enrollees. Here we describe our methods for drive time and distance estimation, review the computational and processing challenges we faced, and present our plans for analyzing the new data.